Cyclooxygenase-2 (COX-2) is highly up-regulated in cancer cells (Rizzo M.T (2011) Clin. Chim. Acta. 412: 671-687) and has been reported to be one of the best prognostic indicators for some cancers (An et al., (2002) Photochem. Photobiol. 76: 73-80). Imaging agents based on the well-characterized COX-2 inhibitors can be used for the early detection of skin cancer and help define tumor margins. It has previously been shown in a genetically engineered mouse model of non-melanoma skin cancer (NMSC) that systemic administration of (1 mg/kg) 5-Rox-D-indomethacin (Fluorocoxib) enabled visualization of small (approximately 100 μm) tumors (FIG. 1, arrows). A continuing problem is the detection of small tumors that are indistinguishable over non-specific background fluorescence.